Field of the Invention
The present invention relates to a probe that is used as a photoacoustic probe for receiving photoacoustic waves caused by an object owing to light with which the object is irradiated and includes a capacitive electromechanical transducer, and an object information acquisition apparatus using the same.
Description of the Related Art
Conventionally, ultrasonic probes employing transducers made of piezoelectric material (i.e., electromechanical transducers) have been used. In recent years, capacitive micromachined ultrasonic transducers (CMUT) manufactured using a semiconductor process has been attracting attention. For instance, the capacitive micromachined ultrasonic transducer has cells each including two parallel plane electrodes and a cavity, and can send and receive acoustic waves by allowing a vibration film (membrane), which is on one side and can vibrate, to vibrate. Particularly in an acoustic medium, excellent wide-band characteristics can be easily achieved. In this specification, the acoustic waves are any of sound waves, ultrasound, and photoacoustic waves. For instance, the photoacoustic waves are caused by irradiating the inside of an object with light (electromagnetic waves), such as visible or infrared light.
In the above technological situations, Japanese Patent Application Laid-Open No. 2010-075681 proposes a probe receiving photoacoustic waves with a configuration where an optical reflection member for reflecting light with which an object has been irradiated is set larger than a receiving surface of the probe. Japanese Patent Application Laid-Open No. 2009-272824 proposes a capacitive ultrasonic probe including a protection layer on a vibration film. This probe has a configuration which includes the protection layer on an upper electrode and in which insulating organic material is arranged as protection layer material. In this specification, the vibration film of the membrane and the upper electrode are sometimes collectively called a vibration film.